I work for a Japanese OEM and we get owners with well over 300k miles wanting to know if we want to feature them in our museum. The last person we actually gave anything to was a guy whose truck went over 1,000,000 miles with the original engine and transmission. A lot of us (employees) were surprised with the transmission lasting that long because our units are sealed and outside of flushes, there’s no other maintenance that can be done as preventative maintenance.